*!*«*" 


THE 

THERMOMETE 

.AND       ITS 

FAMILY 
TRE  E 


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THE 


ITS 

K/VMILJV 
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PUBLISHED  BY 

TAYLOR  INSTRUMENT  COMPANIES 
MANUFACTURERS  OF  METEOROLOGICAL  INSTRUMENTS 
ROCHESTER,  N.Y.  U.  S.  A. 


"V  o 


Copyright  1914 

by 

Taylor  Instrument  Companies 
Rochester,  N.  Y. 


THE:  R,:MOMETER, 


IN  looking  at  a  thermometer — apparently  a  glass  tube  contain- 
ing either  quicksilver  or  a  coloured  liquid  and  placed  upon  a 
divided  and  figured  plate  of  some  description — one  is  not  apt 
to  realize  the  thought,  skill  and  research  it  has  taken  to  bring  this 
simple,  yet  universally  necessary  article  to  its  present  status. 

For  many  centuries  scientists  have  worked 
in  an  endeavor  to  perfect  it,  but  only  during 
the  past  forty  years  have  they  found  out  all 
the  details  necessary  to  the  manufacture  of  a 
more  or  less  perfect  article. 

Many  people  are  credited  with  its  inven- 
tion, Drebbel,  a  Hollander,  being  referred  to 
more  than  any  other,  but  to  Galileo  Galilei  the 
laurels  should  be  handed. 

According  to  history  it  seems  that  about  1592 
he  invented  at  Padua  an  instrument  described 
as  "a  glass  containing  air  and  water,  to  indi- 
cate changes  and  differences  in  temperature." 

With  the  idea  started, 
the  Grand  Duke  of  Tus- 
cany investigated  this 
"invention,"  and  more  or 
less  perfected  it  between 
1630  and  1640. 

The  original  thermometer  consisted  of  a 
glass  tube  about  16  inches  in  length  with  a 
hollow  ball  or  bulb  fitted  at  the  end.  The 
whole  was  heated  until  the  air  inside  be- 
came rarified,  when  the  open  end  was  placed 
in  water,  the  tube  being  kept  upright. 

As  the  air  in  the  tube  cooled  or  con- 
tracted, the  fluid  (water  was  originally 
used)  in  the  tube  rose  to  a  certain  point  and 

anv  subsequent  changes  caused  the  level  of 

.1  *   n    .-i   .      .,  THE  SAXCTORIUS 

the  fluid  in  the  tube  to  be  either  elevated  or          THERMOMETER 

depressed.  ABOUT  1620 


THE  DREBBEI. 

THERMOMETER 

ABOUT   1592 


3O2RRQ 


This  was  used  by  Sanctorius  as  a  "heat  measure"  or  fever 
thermometer.  It  is  on  record  that  he  had  his  patients  hold  the 
top  of  the  "thermometer"  so  the  level  of  the  fluid  would  be 
arrested  at  a  point  equal  to  the  temperature  of  the  person  hold- 
ing it.  A  "point"  was  undoubtedly  determined  by  a  normal, 
healthy  person  beforehand  and  it  is  reasonable  to  assume  that 
Sanctorius  drew  his  deductions  by  noting  the  distance  above  or 
below  this  "normally  healthy"  point. 

M.  Jean  Roy,,  a  French  physician  of  note,  made  a  thermometer 
similar  to  the  one  originally  designed  by  Drebbel,  but  filled  it 
with  alcohol  instead  of  water.  He  did  not  invert  his  "thermom- 
eter" but  kept  it  in  an  upright  position  and  noted  the  rise  and 
fall  of  the  spirit  due  to  the  expansion  or  contraction  of  it.  This 
was  about  1630. 

Before  ten  years  had  passed,  the  Grand  Duke  of  Tuscany 
had  carried  out  his  idea  of  first  partly  filling  the  tube  with 
alcohol  and  closing  the  open  end,  thus  sealing  it  and  excluding 
the  air. 

Realizing  that  the  level  of  the  liquids  in  these  various  instru- 
ments meant  nothing,  pupils  of  Galileo  sought  to  make  a  scale 
of  temperature  and  melted  on  to  the  tube  of  their  thermometers 
small  glass  balls  about  the  size  of  a  pin's  head,  the  zero  of  the 
"scale"  being  the  point  to  which  the  liquid  fell  in  a  freezing 
mixture  of  salt  and  water. 

For  the  next  hundred  years  or  so  the  deepest  confusion 
occurred,  for  not  only  had  various  types  of  instruments  been 
invented,  but  no  two  of  them  agreed  as  regards  their  graduation. 
Many  schemes  and  devices  were  used  to  determine  satisfactory 
scales,  but  agreement  could  not  be  easily  made. 

In  a  book  written  in  1738  by  Bernandinus  Teleius  great 
attention  is  given  to  this  matter. 

At  one  time,  it  seems  the  bright  minds  of  Europe  decided  that 
the  freezing  point  of  liquors  varied  to  such  an  extent  that  it 
could  not  be  used  as  a  test  point,  and  suggested  taking  the 
temperature 

"In  a  carte  cut  straight  into  the  bottom  of  a  cliff  front- 
ing the  sea  to  the  depth  of  130  feet,  with  80  feet  of  earth 
above  it." 
Speaking  of  this,  the  author  says: 

"But  with  Dr.  Hole's  leave,  this  degree  of  tempera- 
ture I  do  not  think  a  very  convenient  term  for  universal 
construction  of  thermometers.  Everybody  cannot  go  to 
Mr.  Boyle's  grotto;  and  it  is  but  few  who  can  have  an 
opportunity  of  making  observations  and  adjusting  ther- 
mometers in  the  cave  of  the  'Parisian  Observatory.' '' 

4, 


In  speaking  of  the  scale  laid  out  by  Sir  Isaac  Newton  as 
having  test  points  at  freezing  water,  the  heat  of  the  human  body,, 
boiling  water  and  melting  tin,  he  says: 

"I  wish   the  world  would  have   received  this   or  any 

other  determined  scale  for  adjusting  their  thermometers, 

but  I  suppose  they  might  be  apprehensive  of  some  incon- 
venience in  this  scheme." 

Robert  Hooke  and  Hon.  Robert  Boyle,,  of  the  "Royal  Society 
in  London/'  were  the  first  to  realize  the  necessity  of  having  a 
standard  scale.  About  1662,  Hooke,  placing  his  instrument  in 
freezing  distilled  water,  marked  "zero"  at  the  top  of  the  column 
of  spirit  after  immersion  of  the  bulb.  Soon  after,  he  suggested 
that  the  second  point  should  be  the  boiling  point  of  water;  but 
this  does  not  seem  to  have  been  adopted  at  that  time. 

Delance  suggested  that  the  freezing  point  of  water  should 
be  marked  "cold"  (-10°),  the  melting  point  of  butter  "hot" 
(-(-10°),  and  the  space  midway  between  "temperate"  (0°),  with 
ten  divisions  between  each. 

In  1714,  Fahrenheit  of  Dantzig  designed  a  scale  for  ther- 
mometers which  showed  the  freezing  of  water  at  32°  and  the 
boiling  of  water  at  212°. 

Many  suggestions  have  been  made  as  to  why  he  graduated 
the  freezing  and  boiling  of  wrater  into  180  divisions,  one  being 
that  as  he  was  an  astronomical  instrument  maker,  and  as  his 
machines  divided  to  full  circles  (360  divisions),  he  used  a  half 
circle  for  his  scale. 

Seventeen  years  later,  Reaumur,  a  French  physicist,  designed 
a  scale  on  which  the  freezing  point  of  water  appeared  as  0 
degrees,  the  scale  between  this  and  the  boiling  of  water  being 
divided  into  eighty  equal  parts. 

Anders  Celsius,  Professor  of  Astronomv  at  the  University  of 
Upsala,  proposed  a  scale  in  1742,  and  called  the  freezing  point 
of  water  100°  and  the  boiling  point  of  water  0.  These  points 
were  afterwards  reversed  by  Christin  of  Lyons  (France)  in 
1743,  and  the  result  is  the  well  known  Centigrade  scale. 

Athanasius  Kircher  was  the  first  to  use  quicksilver  in  ther- 
mometers, although  Delance  once  remarked  "curious  people  use 
it,"  little  dreaming  that  one  day  it  would  become  universal  in 
use. 

In  speaking  of  the  faults  of  different  liquids  used  in  the  early 
manufacture  of  these  instruments  Teleius  remarks: 

"We  have,  it  seems,  nothing  left  but  quicksilver. 
"This  is  a  very  movable,  and  ticklish  fluid;  it   both 

heats  and  cools  faster  than  any  liquor  we  know  of  or  have 

had  occasion  to  try." 

5 


Quicksilver  and  alcohol  have  been  accepted  by  the  scientific 
world  as  a  convenient  and  accurate  means  to  indicate  the  tem- 
perature of  anything  with  which  the  tube  containing  them  may 
come  in  contact. 

For  high  temperatures  quicksilver  is  used,  for  it 

FREEZES  AT  -38°  Fahrenheit,  -38°  Centigrade 
AND  BOILS  AT  674.6°  Fahrenheit,  -357°  Centigrade 
As  the  freezing  point  of  mercury  is  fairly  high,,  alcohol  ther- 
mometers   are    invariably   used    in   very    cold    climates,,    for   this 
liquid 

FREEZES  AT  -202.9°   Fahrenheit,  -130.5°  Centigrade 
AND  BOILS  AT  173.5°  Fahrenheit,  78.5°  Centigrade 
From  this  it  will  be  seen  that  quicksilver  is  unsuitable  for  any 
very  low  temperature  and  alcohol  is  unsuitable  for  any  very  high 
temperature. 


THE  CONVERSION  OF  THERMOMETER  SCALES 

Centigrade  to  Fahrenheit 

To  convert  Centigrade  degrees  to  degrees  of  Fahrenheit, 
multiply  by  9,  divide  the  product  by  5  and  add  32.  When  the 
temperature  Centigrade  is  below  0  Cent,  deduct  32  instead  of 
adding. 

Fahrenheit  to  Centigrade 

To  convert  Fahrenheit  degrees  to  degrees  of  Centigrade,  sub- 
tract 32,  multiply  by  5  and  divide  by  9.  When  the  temperature 
Fahrenheit  is  below  0  Faht.  add  32  instead  of  subtracting. 

Reaumur   to   Fahrenheit 

To  convert  Reaumur  degrees  to  degrees  of  Fahrenheit,  multi- 
ply by  9,  divide  by  4  and  add  32.  When  the  temperature 
Reaumur  is  below  0  Reau.  deduct  32  instead  of  adding. 

Reaumur   to   Centigrade 

To  convert  Reaumur  degrees  to  degrees  of  Centigrade,  multi- 
ply by  5  and  divide  by  4. 

Centigrade   to  Reaumur 

To  convert  Centigrade  degrees  to  degrees  of  Reaumur,  multi- 
ply by  4  and  divide  by  5. 

C         Water  Freezes  at  0°  77*         Water  Freezes  at  32° 

ent.       "       Boils        "  100°          JT  aht.       "       Boils        "  212° 

Water  Freezes  at  0° 
.eaumur        "      Boils        "   80° 


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THE  THREE  STANDARD  SCALES  FOR  THERMOMETERS 


THE  MAKING  OF 
GLASS  THERMOMETER  TUBING 

As  the  value  of  a  thermometer  depends  to  a  great  extent  on 
the  grade  of  glass  and  the  care  taken  in  making  and  drawing  it 
into  the  tubes,  a  few  words  regarding  it  will  be  of  help  to  the 
reader  and  will  give  an  idea  of  how  the  small  "hole"  or  "bore" 
up  which  the  quicksilver  travels,  is  formed  in  the  glass. 

Glass  is  hard,  brittle  and  transparent.  It  is  formed  by  fus- 
ing together  mixtures  of  silicates  of  potash,  soda,  lime,  magnesia, 
alumina  and  lead  in  various  proportions,  according  to  the  quality 
or  kind  of  glass  required. 

The  first  step  in  the  manufacture  of  glass  tubing  is  to  take  an 

iron  pipe,  about  five 
feet  long  and  collect 
on  about  two  inches  of 
the  end  of  it  (by 
dipping  it  in  molten 
glass)  a  quantity  of 
glass  about  as  large 
as  a  quart  milk  jug. 
When  this  glass  is 
still  in  a  plastic  state 
(i.  e.,  not  hard)  a 
bubble  is  formed  in 
the  centre  of  it  by 
blowing  hard  into  the 
end  of  the  iron  pipe. 
The  glass  is  then 
rolled  over  a  plate  so 
it  becomes  cylindrical 
in  shape  (like  the 
tubular  record  of  a 
phonograph)  but 
solid,  except  for  the 
hole  in  the  centre 
caused  by  blowing 
through  the  iron  pipe. 

This  rolling  process  causes  the  roughly  blown  round  hole  in  the 
glass  to  attain  a  cylindrical  shape — more  or  less  perfect  in 
appearance. 

The  next  process  is  to  flatten  the  glass,  which  is  accomplished 
by  applying  pressure  to  the  top  and  bottom  of  the  mass.  This 
operation  causes  the  cylindrical  hole  in  the  centre  to  flatten  out 
a  trifle,  due  to  pressure,  and  to  appear  in  the  shape  of  a  thick 
ribbon  instead  of  a  circular  hole. 

8 


ROLLING  THE  GLASS  MASS 


White  enamel  glass  is  then  put  on  that  part  of  the  tube  which 
is  directly  behind  the  "hole"  or,  as  it  is  called  in  the  finished 
thermometer,  the  "bore." 

The  mass  is  now  put  into  hot  glass  so  it  is  absolutely  covered 
with  a  new  coat  of  it.  During  all  these  processes  the  glass 
develops  "waviness"  and  to  get  it  into  proper  condition  and 
solidity  it  has  to  be  rolled  on  iron  slabs.  The  outside  is  chilled 
somewhat,  so  the  inside  retains  its  correct  shape. 

In  order  to  properly  read  the  quicksilver  in  the  column,  a 
great  many  tubes  have  "lens"  fronts.  This  lens  is  formed  on  the 
glass  by  putting  it  in  a  "V"  shaped  mould  with  the  white  enamel 
glass  uppermost.  The  mass  then  represents  a  wedge  with  a 
rounded  top. 

Now  remember  what  has  been  done  to  this  glass  to  make 
tubing  from  it.  A  hole  has  been  blown  in  the  centre  of  the 
original  "lump"  of  glass ;  it  has  been  rolled  out,  flattened  on  the 

top  and  on  the  bottom,  it  has  had 
white  enamel  put  upon  the  back,  and 
has  been  covered  with  a  second  coat- 
ing of  glass.  Finally  it  has  been 
rolled  again  to  take  imperfections 
out  and  then  the  lens  has  been 
formed  on  the  front. 

At  this  point  it  looks  like  a  piece 
of  glass  tubing  about  5  inches  thick 
and  9  inches  long,  on  the  end  of  an 
iron  tube  with  a  long  bubble  in  the 
centre,  some  white  glass  behind  the 
bubble  and  the  glass  formed  in 
a  "V"  or  wedge  in  front  of  the 
bubble. 

Now  the  delicate  operation  comes 
of  "pulling  this  glass  out" — or 
"stretching"  it  into  the  small  thin 
canes  of  tubing  such  as  are  used  in 
thermometer  making. 

The  mass  of  glass  is  put  on  a  hot 
iron  plate — six  or  eight  inches  in 
diameter,  with  the  iron  tube  through 
which  the  hole  was  blown  pointing 
upwards.  This  tube  is  secured  to  a 

wire    cable    extending    upwards    for    about    150    feet,    which    is 

attached  to  a  motor. 

The  glass   is  now  ready  and  the  motor  is  put  in  operation, 

9 


DRAWIXG  PLASTIC  GLASS 
IXTO  TUBES 


with  the  result  that  the  plastic  glass  is  pulled  upwards  for  about 
150  feet  into  a  more  or  less  perfect  tube. 

The  hole  which  was  originally  blown  in  the  centre  becomes 
the  minute  hole  up  and  down  which  the  quicksilver  travels ; — the 
white  enamel  glass  becomes  the  white  back  of  the  thermometer 
tube,  and  the  "V"  front  becomes  the  magnifying  lens. 

The  tubing  is  now  ready  for  cutting  up  into  "canes,"  or 
lengths  of  glass,  to  be  used  for  tube  making.  The  ends  of  the 
length  after  drawing  are  useless,  due  to  distortion  in  forming  them. 

Great  care  has  to  be  taken  in  sorting  this  glass,  for  the  size 
of  the  hole  or  "bore"  in  the  centre  of  the  glass  varies,  and  as 
a  consequence  quicksilver  or  spirit  will  rise  slowly  up  a  tube  hav- 
ing a  large  bore,  and  quickly  up  a  tube  having  a  small  bore,  if  the 
bulb  or  quicksilver  ends  of  the  thermometer  are  of  the  same  size. 


A 

| 

B 


A     THERMOMETER  BORE 
B     HUMAX  HAIR 

In  some  thermometers  the  "bore"  is  very  much  finer  than  the 
diameter  of  a  human  hair,  and  the  relation  of  the  capacity  of  the 
bulb  which  holds  the  quicksilver  to  the  tube  up  and  down  which 
it  travels,  is  roughly  1000  to  1. 

The  "grading"  of  these  tubes  calls  for  the  work  of  an  expert, 
for  it  can  only  be  done  by  putting  the  end  of  the  glass  to  a 
powerful  microscope  and  measuring  the  "bore"  by  means  of  hair 
lines  under  magnification. 

This  practically  completes  the  making  of  glass  tubing. 

THE  MAKING  OF  THE  THERMOMETER  TUBE 

The  lengths  of  glass  tube,  or  "canes"  as  they  are  called,  are 
now  cut  into  pieces  twice  the  size  of  the  thermometer  into  which 
they  will  ultimately  be  turned. 

The  sharp  flame  of  a  blow  pipe  is  made  to  play  in  the  centre 
of  the  tube.  When  it  has  become  warm  enough  it  can  be  pulled 
apart,  making  two  complete  tubes,  each  of  the  same  size  and  each 
sealed  at  one  end. 

10 


MEASURING  THE  BOBE  OF  A  TUBE 

One  of  these  tubes  is  now  taken  and  an  ordinary  rubber  bulb 
is  fitted  to  the  OPEN  end. 

The  CLOSED  end  is  now  heated.,  pressed  and  manipulated  until 
the  glass  is  more  or  less  solid  at  this  end.  If  the  rubber  bulb  is 
now  pressed,  air  is  forced  down  the  tube  and  when  it  reaches 
the  molten  end  a  bubble  is  formed.  This  bubble  is  called  the 
bulb.  (See  illustration  page  13). 

In  the  manufacture  of  thermometers  of  anything  above  good 
grade,  special  hard  glass  is  melted  on  to  the  end  of  the  tube,  so 
that  the  bulb  is  formed  from  this  glass  instead  of  from  the  tube 
glass. 

Sometimes  these  bubbles  or  bulbs  are  made  large  and  some- 
times small — it  all  depends  on  what  is  required  of  the  finished 
thermometer.  If  the  bore  in  the  tube  is  large  and  the  bulb 
large,  or  if  the  bore  in  the  tube  is  small  and  the  bulb  is  small,  the 
quicksilver  will  rise  much  more  slowly  in  the  tube  than  if  the  bore 
is  small  and  the  bulb  large. 

Every  tube,  therefore,  having  a  certain  bore  must  have  a  cer- 
tain sized  bulb  to  make  it  work  in  a  particular  manner.  If  it 
were  required  to  create  a  thermometer  in  the  Fahrenheit  scale 
with  the  "freezing"  at  a  certain  point — say  \ff  from  the  bulb, 
and  a  120°  point,  say  J"  from  the  top  of  the  tube,  the  bore  of  the 
tube  would  have  to  be  measured  and  the  bulb  would  have  to  be  of 
a  certain  exact  size. 

It  is  possible  with  a  microscope  to  measure  the  bore 
accurately  and  it  is  possible  to  determine  the  size  the  bulb  should 

11 


FILLIXG  A  TUBE  WITH  QUICKSILVER 

be,  but  it  is  impossible  to  make  it  work  so  that  at  certain  tempera- 
tures the  quicksilver  would  stand  at  a  number  of  predetermined 
points  on  the  tube. 

Plates  having  different  sized  holes  in  them  are  supplied  to 
the  tubemakers  and  with  the  workman's  knowledge  of  the  size  of 
the  bore,  the  approximate  size  of  the  bulb  can  be  determined 
when  they  know  the  lowest  point  and  the  highest  point  the 
thermometer  will  be  required  to  register.  For  instance,  a  bulb 
\"  in  diameter  might,  if  fitted  to  a  tube  having  a  certain  bore, 
have  a  range  of  scale  showing  200°  from  its  highest  point  to  its 
lowest  point.  If  the  bulb  was  made  \"  in  diameter,  the  range 
of  scale  might  be  equal  to  50°. 

After  the  bulb  has  been  formed  to  the  correct  size,  and  while 
it  is  still  hot,  the  open  end  of  the  tube  is  placed  in  a  jar  of  pure, 
clean  quicksilver.  As  the  glass  cools,  the  air  in  the  bulb  and 
tube  contracts,  drawing  the  quicksilver  up  into  it. 

This  process  will  only  partially  fill  the  tube  and  in  order  to 
complete  it,  the  tube  after  cooling  is  taken  out  of  the  jar,  and 
with  the  bulb  downwards  more  heat  is  applied,  when  it  is 
again  inverted  in  the  jar  and  so  on,  until  the  bulb  and  tube  are 
completely  filled. 

A  process  known  as  "roasting"  is  carried  on,  to  expel  every 
particle  of  moisture. 

In  order  to  properly  seal  and  close  the  tube,  a  gas  flame  is 
blown  across  the  top  of  it  until  the  glass  becomes  very  plastic. 

12 


BLOWIXG  AXD  GAUGING  THE  BULB 

The  top  of  the  tube  is  now  drawn  away  in  exactly  the  same  way 
as  it  is  drawn  in  the  original  manufacture— very  thin — but  still 
having  a  very  minute  hole  or  bore  in  the  centre. 

Heating  the  bulb  again  drives  the  quicksilver  to  the  top  of  the 
tube  once  more  and  it  travels  along  the  newly  made  thin  tube, 
expelling  all  the  air.  If  the  glass  at  the  extreme  top  of  the  main 
tube,  or  at  that  portion  of  it  which  starts  to  thin  out  by  the  last 
operation,,  be  melted,  it  will  seal  this  hole  and,  providing  the 
operation  is  accomplished  carefully,  will  prevent  any  air  from 
entering  the  thermometer,  and  the  quicksilver  will  flow  back  to 
the  bulb  of  the  tube  as  it  cools. 

This  end,  or  hook  as  it  is  called,  is  used  to  securely  fasten  the 
thermometer  tube  to  its  scale. 

The  thermometer  tube  is  now  complete,  for  a  bulb  has  been 
formed  at  the  end,  the  tube  and  bulb  have  been  filled  with  quick- 
silver, the  air  expelled  and  the  end  sealed.  The  quicksilver  is 
now  free  to  move  up  and  down  the  tube  as  soon  as  temperature 
changes  either  expand  or  contract  it.  When  the  surrounding  air 
gets  warmer  the  quicksilver  expands  and  rises  in  the  tube  and 
when  the  surrounding  air  gets  cooler  it  contracts  and  falls. 

Although  we  have  our  tube,  bulb  and  quicksilver  made  satis- 
factorily, we  have  not  a  thermometer,  because  the  height  of  the 
quicksilver  in  the  tube  for  any  temperature  has  not  yet  been 
determined. 

To  properly  accomplish  this  it  is  necessary  to  have  water  in 
receptacles  of  different  temperatures,  one  at  32°  Faht.,  one  at 
62°  Faht.,  and  another  at  92°  Faht ,  if  the  thermometer  is  to  be 
used  for  ordinary  living  or  room  temperature. 

13 


The  32°  Faht.  point  is  obtained  by  crushing  ice,  as  32°  Faht. 
is  the  temperature  of  either  freezing  water  or  melting  ice.  A 
point  2°  Faht.  is  obtained  on  some  thermometers,  being  reached 
by  a  brine  solution. 

In  each  of  these  "baths"  a  thermometer  of  known  accuracy  is 
placed  and  left  immersed  a  sufficient  time  to  enable  the  quick- 
silver to  come  to  rest,  thus  determining  the  correct  temperature 
of  the  water,  which  must  be  constantly  agitated,  in  order  to  keep 
it  from  becoming  cooler  on  the  sides  than  in  the  centre,  or  vice 
versa. 

Water  in  thermometer  manufacturing  is  mechanically  con- 
trolled at  the  necessary  temperatures,  but  if  by  chance  it  should 
rise  or  fall  below  the  desired  point,  it  can  be  readily  adjusted  by 
introducing  either  cold  water  or  steam,  dependent  on  the  condi- 
tion of  it. 

If  the  bath  is  controlled  and  has  a  temperature  of  62°  Faht., 
the  thermometer  tube  which  has  to  be  tested  is  put  in  and,  when 
the  quicksilver  has  come  to  rest,  a  line  is  put  upon  the  tube  at  the 
level  of  the  quicksilver,  thus  indicating  the  point  at  which  the 
quicksilver  stands  when  the  temperature  is  at  62°  Faht.  This 
operation  is  repeated  in  a  bath  of  92°  Faht.,  and  also  in  crushed 
ice  at  32°  Faht.  A  point  2°  above  zero  Fahrenheit  is  reached  in 
cold  brine. 

Four  marks,  divisions,  or  "points"  as  they  are  called,  have  now 
been  determined  and  if  they  are  equidistant  it  is  reasonable  to 
assume  that  each  can  be  sub-divided  into  thirty  equal  divisions, 
i.  e.,  from  2  to  32,  from  32  to  62,  and  from  62  to  92.  The  divi- 
sions can  be  extended  below  2  and  above  92  at  the  same  ratio  with 
reasonable  accuracy. 

A  brass  plate  is  now  taken,  which  when  completed  will  form 
the  scale  or  face  of  the  thermometer,  for  upon  it  the  graduations 
have  to  be  placed, — also  the  figures. 

The  thermometer  -tube  is  set  upon  this  plate  and  the  marks 
which  denote  2°,  32°,  62°,  and  92°  Faht.,  are  reproduced  in 
exactly  the  same  positions  upon  it.  A  dividing  machine  is 
arranged  to  cut  or  engrave  the  necessary  divisions.  It  can  be 
finished  in  any  desired  style  and  the  thermometer  tube  perma- 
nently placed  upon  it.  Great  care  must  be  exercised  in  seeing 
that  the  points  on  the  tube  agree  exactly  with  the  same  points  on 
the  scale. 

This  practically  completes  a  common  tvpe  of  thermometer. 
Refinements  in  manufacture  are  many  and  there  are  various  and 
obvious  reasons  why  a  thermometer  apparently  looking  the  same 
as  another  should  cost  two,  three  or  even  four  times  as  much. 

14 


ERRORS  WHICH  MUST  BE  GUARDED  AGAINST 

MANUFACTURING 

(A)  Careless  "pointing"  of  the  tube  will,  of  course,  result  in 
erroneous  readings  and  it  is  one  of  the  most  common  sources  of 
trouble  in  practical  thermometrv. 

This  can  be  caused  through  inefficient  labour,  through  care- 
lessness in  placing  the  points  upon  the  tube,,  or  in  letting  the  test 
baths  get  either  too  cool  or  too  warm,  during  the  pointing  process. 

Occasionally  the  thermometer  tube  will  slide  from  its  position 
on  the  scale  and  naturally  all  indications  will  be  reading  either 
above  or  below  the  true  reading. 

(B)  If  the  bore  of  the  tube  is  erratic,  the  quicksilver  will 
naturally  rise  more  slowly  in  parts  which  are  larger,  and  faster  in 
parts  which  are  smaller. 

The  theory  of  this  was  pointed  out  on  page  11,  which  ex- 
plained the  connection  between  the  bulb  and  the  bore.  The 
smaller  the  bore  the  quicker  the  rise  of  the  quicksilver  in  the  tube. 

(C)  Impurities  in  the  quicksilver  make  the  bore  of  the  tube 
rough  and  if  the  quicksilver  is  dusty,  particles  of  it  will  stick  to 
the  bore  of  the  tube,  and  besides  being  unsightly  it  will  cause  the 
quicksilver  to  appear  sluggish  in  its  action. 

(D)  As  glass  shrinks  after  manufacture,  it  is  necessary  in 
order  to  have  a  thermometer  keep  its  readings  correct,  to  make 
sure  the  glass  is  properly  "seasoned." 

The  shrinkage  of  glass  is  imperceptible,  but  it  is  easy  to 
realize  that  if  the  bulb  and  bore  of  the  tube  contract  the  smallest 
amount,  the  quicksilver  will  be  driven  higher  in  the  tube,  so  that 
a  point,  say  40°  Faht.,  might  be  correct  on  the  scale  made  for  the 
tube  when  new,  but  after  the  tube  had  contracted,  or  shrunk,  or 
become  seasoned,  might  read  46°  Faht.,  or  even  48°  Faht., 
depending  on  the  quality  of  the  glass.  The  only  way  to  over- 
come this  is  to  keep  tubes  in  storage  for  eighteen  or  even  twenty- 
four  months  before  determining  the  "points,"  so  that  all  contrac- 
tion of  the  glass  will  have  passed  and  the  indications  will  be 
permanently  accurate. 

15 


BLUNDERS  WHICH  CAN  BE  AVOIDED 

OBSERVING 

(A)  Nothing  is  so  disheartening  to  an  observer  of  tempera- 
ture, whether  he  be  noting  temperature  of  a  room,  the  soil,  the 
outside   air,   or  whatnot,  as   readings   which   he   feels   he  cannot 
rely  on. 

Naturally  it  is  essential  in  the  first  place  that  the  thermometer 
being  used  is  of  known  accuracy  and  will  remain  so.  A  little 
extra  cost  in  the  original  purchase  of  a  thermometer  will  never 
be  regretted. 

(B)  All  thermometers   are  affected  by  the  surrounding  air. 
When  observing  the  readings  be  careful  not  to  stand  so  near  the 
bulb   that  it  will  be   affected  by  the  warmth  of  your  body  or 
breath.      This  is  a  continual  source  of  trouble,  especially  if  the 
thermometer.be  a  very  sensitive  one. 

(C)  Take  great  care  in  noting  the  proper  division  on  the 
scale.      Some  thermometers  have  their  divisions  in  2°  lines,  some 
in  1°  lines,  some  in  ^°  lines  and  some  in  1-5°,  1-10°,  etc.      Errors 
are  often  made  in  reading  2°  lines  as  1°  lines. 

(D)  In  reading  be  sure  and  get  the  eye  level  with  the  quick- 
silver.     If  you  read  it  from  below  the  reading  will  appear  too 
high,  and  if  from  above  too  low. 

(E)  In  moving  a  thermometer  into  a  fresh  place  remember 
it  takes  some  time  for  it  to  adjust  itself  to  the  new  temperature. 
This,  of  course,  depends  on  the  sensitiveness  of  the  instrument. 
Fanning   it,   or   passing   it   carefully   through   the   air    for    some 
time  will  greatly  help  it. 

(F)  Beware  of  the  word  "Standard  !"      It  is  a  most  abused 
term !      The  word  is  placed  on  some  thermometers  that  are  not 
standard  in  any  sense  of  the  word.      In  experience  the  writer  has 
found  thermometers  marked  this  way  with  errors  varying  from 
3°  to  10°  Faht. 

(G)  Do    not    condemn    a    thermometer   because    it    does    not 
agree  with  one  hung  near  it.      Remember  these  instruments  indi- 
cate the  temperature  of  the  air  which  surrounds  THEM  and  NOT 
the  temperature  of  the  air  one  inch  or  twelve  inches  away. 

16 


TYPES  OF  THERMOMETERS 


The  style  of  thermometer  ordinarily  used  for  the  purpose  of 

determining  the  temperature  of  rooms,  offices,  corridors,  etc.,  is 

that  having  a  metal  plate  with  the  thermometer  tube  set  upon  it, 

the  whole  being  fitted  to  a  wooden  back,  of  varied 

styles  and  descriptions. 

Such  a  thermometer  is  very  satisfactory,  pro- 
viding it  is  not  influenced  by  direct  sunshine, 
draughts,  open  windows,  radiators,  air  furnaces, 
etc.  Care  should  be  taken  when  fitting  it  on  the 
wall  to  see  that  no  chimneys  or  air  shafts  pass 
through  that  part  of  the  wall,  causing  it  to  be  exces- 
sively hot  or  cold.  When  convenient  a  thermometer 
should  be  set  two  or  three  inches  away  from  a  wall, 
so  that  it  may  get  correct  circulation  of  air  around  it. 
The  most  satisfactory  height  for  a  room  ther- 
mometer is  about  60  inches  to  70  inches  above  the 
floor.  Thermometers  having  coloured  alcohol  in  them 
in  place  of  quicksilver  can  be  much  more  quickly 
read,  but  they  are  somewhat  sluggish  in  their  work- 
ing, compared  to  those  in  which  quicksilver  is  used. 
Sometimes  the  alcohol  may  become  separated 
from  the  main  column,  but  it  can  be  easily  joined  to 
ROOM  **  ky  swinging  the  thermometer  sharply  backwards 

THER-          and  forwards  with  a  pendulous  motion,  taking  care 
MOMETER        that  the  bulb  is  downwards.     It  is  also  desirable  to 
occasionally  examine  the  upper  part  of  the  tube  and 
to  see  that  it  is  perfectly  free  from  detached  portions  of  alcohol. 
An  easy  method  of  correcting  this  is  to  take  the  thermometer  with 
the  bulb  in  the  right  hand  and  strike  the  top  against  the  palm  of 
the  left  hand.      The  alcohol  at  the  top  of  the  tube  will  slowly 
start  to   run  down  towards   the  main  column.      When  detached 
portions  are  joined,  the  thermometer  should  be  allowed  to  stand 
in  an  upright  position  for  about  half  an  hour. 

This  simple  form  of  thermometer  gives  indications  of  existing 
temperatures.  In  sick  rooms,  greenhouses  and  many  other 
places,  it  is  interesting  and  sometimes  necessary  to  have  a  knowl- 
edge of  what  the  temperature  has  been.  For  this  purpose  a  ther- 
mometer capable  of  giving  maximum  and  minimum  temperatures 
is  used.  The  one  most  common,  interesting,  and  effective  is  a 
pattern  designed  by  Mr.  James  Sixe,  of  Canterbury,  England. 
It  consists  of  a  glass  "U"  shaped  tube  with  the  ends  terminating 
sometimes  in  round  balls  and  sometimes  in  a  ball  at  one  end  and 
a  glass  cylinder  at  the  other.  The  latter  pattern  is  in  all  ways 

17 


preferable.  The  tube  is  completely  filled  with  creosote  to  within 
almost  one-half  inch  of  its  top,  which  is  filled  with  air.  Prior  to 
this  quicksilver  has  been  put  into  the  lower  portion  of  the  "U," 
but  NOT  for  the  working  member,  as  popularly  supposed. 

If  the  illustration  be  examined  it  will  be  found  that  the  left 
side  scale  is  figured  from  120°  at  the  bot- 
tom to  40°  at  the  top,  while  the  right  hand 
side  is  practically  the  reverse  of  this. 

The  creosote  in  the  tube  in  the  centre 
expands  when  the  temperature  increases, 
driving  the  quicksilver  down  on  the  left 
hand  side  and  up  on  the  right  hand  side, 
thus  increasing  the  air  pressure  in  the  right 
hand  bulb.  As  th.e  right  hand  side  shows 
an  increase  in  its  scale  reading  it  is  called 
the  "Heat  or  Maximum"  side  of  the  tube. 

If  the  temperature  lessens,  the  creosote 
will  contract  so  that  the  quicksilver 
will  fall  on  the  "Heat"  side  and  rise 
on  the  "Cold"  or  "Minimum"  side, 
which  shows  the  thermometer  scale 
decreasing. 


Indices  are  carefully  made  and 
inserted  in  the  tubes  above  the  levels  of  the 
quicksilver,  so  they  can  be  used  to  indicate 
the  highest  and  lowest  point  the  thermometer 
has  reached  since  its  last  setting. 

The  index  is  a  miniature  glass  bottle  with 
a  small  piece  of  steel  wire  inside  it.  Steel  is 
used  so  that  the  index  can  be  raised  or 
lowered  by  means  of  a  magnet,  which  can  be 
moved  up  and  down  in  front  of  the  tube.  In 
order  to  keep  the  index  from  receding  with 
the  quicksilver,  two  hair-like  appendages  are 
fitted  to  it  (one  of  these  is  fastened  to  the 
bottom  and  points  upwards,  the  other  is 
fastened  to  the  top  and  points  downwards). 
HIGH  AXD  Low  ^s  ^e  quicksilver  rises  on  either  the  "Heat" 
THERMOMETER  or  "Cold"  side,  the  index  is  raised  on  the  sur- 

"SIXE'S  TYPE"  face  of  it,  and  when  the  quicksilver  recedes 

the  index  remains  stationary  until  reset  with 

a  magnet.  It  will  then  indicate  the  highest  and  lowest  reading 
since  its  last  setting.  Another  type  of  thermometer  to  give 
maximum  and  minimum  temperatures  is  shown  on  page  19. 

18 


HIGH  AXD  Low  THERMOMETERS.     HORIZONTAL  TYPE 

This  consists  of  two  separate  thermometers  set  horizontally, 
one  to  give  maximum  readings  and  the  other  minimum.  The 
maximum  instrument  is  quicksilver-filled,  the  tube  being  arranged 
in  such  a  manner  that  when  the  temperature  cools  the  quicksilver 
cannot,  by  itself,  set  back  into  the  bulb.  This  allows  it  to  remain 
indefinitely  in  the  tube.  In  order  to  reset  it,  it  is  necessary  to 
swing  it  sharply  a  couple  of  times,  when  the  quicksilver  will 
easily  and  quickly  be  driven  back  into  its  bulb. 

The  minimum  thermometer  is  alcohol-filled  and  has  a  small 
index  set  in  the  fluid.  By  holding  the  thermometer  upside  down 
this  index  \vill  flow  down  the  alcohol  to  the  end.  It  should  now 
be  placed  horizontally.  When  the  air  cools  the  alcohol  is  natur- 
ally drawn  toward  the  bulb,  bringing  the  index  with  it.  When  it 
rises  again  the  index  is  left  stationary  in  the  tube,  indicating  the 
lowest,  or  minimum,  temperature.  To  reset  it,  invert  the  ther- 
mometer, when  the  index  will  flow  again  to  the  end  of  the  alcohol 
column. 

As  they  are  of  approved  standard  type,  the  thermometer 
tubes  have  the  temperature  divisions  etched  upon  them.  This  is 
duplicated  every  5°  or  10°  on  the  scale  itself. 

Any  thermometer  marked  "Standard"  and  not  having  its  scale 
divided  and  etched  directly  on  the  tube  itself,  is  not  a  standard 
thermometer.  Standard  thermometers  are  always  accompanied 
with  a  certificate  of  correction  which  shows  the  error  (if  any), 
so  that  true  readings  of  temperature  can  be  arrived  at. 

Thermometers  with  glass  scales  are  made  for  exposure  out- 
side of  windows,  so  that  outside  temperatures  can  be  read  from 
inside. 

The  figures  on  the  scale  are  either  etched  permanently  upon 
the  glass  or  are  painted  upon  it  and  baked  in,  so  that  water,  snow, 
sunshine,  etc,,  will  neither  fade  nor  wash  them  out. 

Such  thermometers  are  usually  fitted  outside  the  window,  the 
metal  arms  allowing  them  to  be  held  far  enough  away  to  prevent 
the  warmth  (in  winter)  from  the  window  affecting  them. 

19 


A  northern  exposure  is  the  best  if  it  can  be  found,  for  the  sun 
will  not  then  upset  the  readings  of  the  instrument,  as  will  be  the 
case  if  it  be  exposed  on  the  south,  where  the  sun  will,  when  out, 
always  shine  upon  it. 

In  some  instances  it  is  necessary  to  have  knowledge  of  what 
the  temperature  has  been  during  any  previous  period,  or  for  any 
particular  time.  An  instrument  known  as  a  "thermograph"  or 
recording  thermometer,  is  used  for  this  purpose. 

Instead  of  using  a  quicksilver  or  alcohol  thermometer  the 
working  part  consists  of  a  spiral  metallic  coil,  which  is  very  sen- 
sitive to  changes  of  temperature.  To  this  coil  is  fitted  an  arm, 
about  seven  inches  long,  to  the  end  of  which  is  fitted  a  pen  which 


RECORDING  THERMOMETER 

registers  on  a  drum  (containing  a  clock)  the  different  changes  as 
they  take  place. 

The  clock  rotates  upon  its  axis  once  a  week  and  has  wrapped 
round  it  a  chart  on  which  are  divided  the  days  of  the  week,  each 
day  being  divided  into  two-hour  spaces. 

20 


^«   -Z&ttt  13  li 

frrshiri  :-'••?; ',  ?  7-'  -••  r -•-•  •  r •  •  -  ~  •  >  ?  • 


1     ;     n      •  •  !•  -    liTiiW 
* 


CHART  OF  RECORDING  THERMO3IETER 

The  pen  on  the  arm  rises  and  falls  as  the  temperature  in- 
creases or  decreases  and  as  the  clock  revolves  a  tracing  is  made 
on  the  chart,  which  also  indicates  the  time  at  which  such  changes 
occur. 

In  a  greenhouse.,  sick  room,  or  anywhere  where  temperature 
is  of  consequence,  the  information  one  gains  by  consulting  the 
ordinary  thermometer  is  not  sufficient,  for  in  the  case  of  the  green- 
house, the  thermometer  early  in  the  morning  may  show  4-5° 
Faht.,  but  who  is  to  know  the  extent  of  its  fluctuations  throughout 
the  night  or  if  it  went  to  or  below  the  freezing  point,  killing  all 
the  young  growth  which  was  being  so  carefully  guarded? 

The  same  applies  to  the  sick  room.  It  can  be  easily  seen  if 
the  temperature  of  the  room  is  being  maintained,  or  if  it  is 
fluctuating  materially. 

Records  can  be  filed  and  kept  for  reference,  for  one  never 
knows  when  such  information  may  be  needed. 

There  is  one  type  of  thermometer  which  can  be  found  in  the 
most  remote  parts  of  the  earth — in  the  frozen  Arctic  and  in  the 
sweltering  tropics, — men  never  travel  without  it.  It  is  used 
among  the  uncivilized  as  well  as  the  civilized,  by  all  races  of 
mankind,  irrespective  of  colour  or  religion.  It  is  called  the 
"fever"  thermometer. 

It  is  a  well  known  fact  that  during  health  the  same  degree  of 
temperature  is  virtually  maintained.  No  matter  whether  it  be 
winter  or  summer  our  bodies  contain  the  same  amount  of  heat  if 
they  be  in  a  normal,  healthy  condition. 

They  not  only  contain  it,  but  do  so  with  a  beautiful  and 
natural  exactness. 

The  temperature  of  a  human  being  is  not  the  same  in  all  parts 
of  the  body,  so,  to  establish  a  common  standard,  the  medical 
fraternity  accepted  the  temperature  as  taken  under  the  tongue. 

21 


In  some  cases  (such  as  in  young  children  and  those  suf- 
fering from  delirium),,  this  is  not  a  practicable  place,,  so  the 
rectum,  or  a  point  under  the  arm  is  selected,  although  the 
latter  is  not  a  very  satisfactory  point  of  contact,  on  ac- 
count of  the  time  the  instrument  takes  to  register  the  maxi- 
mum temperature. 

From  a  vast  number  of  observations,  a  point  98.6°  on 
the  Fahrenheit  scale  has  been  determined 
as  "Normal  health."  If  the  thermometer 
should  rise  or  fall,  or  fluctuate  from  this 
point,  the  delicate  mechanism  of  the  body 
is  in  some  way  deranged.  Some  people 
are  "subnormal"  and  others  are  "abnor- 
mal," meaning  that  their  individual  and 
correct  temperature  is  a  fraction  of  a  de- 
gree below  or  above  the  98.6°  Fahrenheit. 


The 


average,      as    are 


all 
from 


averages, 
good 


was    probably    determined 
many  thousand  readings. 

Fever  thermometers  are  made  to  regis- 
ter the  maximum  temperature  by  leaving 
the  quicksilver  end  under  the  tongue  for  2 
minutes,  1  minute,  or  ^  minute.  The  tube 
is  made  in  such  a  manner  that  while  the 
quicksilver  will  rise  in  the  tube  as  the 
temperature  increases,  it  will  not  "set 
back"  to  the  bulb  after  it  is  taken  from  the 
mouth  and  becomes  exposed  to  a  lower 
temperature.  This  is  called  a  "self-regis- 
tering" feature  and  it  is  necessary  after  each 
observation  to  hold  the  thermometer  firmly  by 
the  upper  end  with  the  bulb  downward  and 
swing  or  shake  it  in  such  a  manner  as  to  force 
the  quicksilver  back  toward  the  bulb. 

The  instrument  should  be  carefully  cleansed 
after  each  reading,  to  prevent  the  spread  of  any 
infection,  and  should  be  kept  in  as  sanitary  a 
case  as  possible. 

Since  a  fever  thermometer  must  be  and  must 
remain  of  absolute  standard  accuracy,  it  is  easy 
to  see  that  good  ones  cannot  be  cheap  in  price 
and  that  they  cannot  be  purchased  for  a  "mere 
trifle." 

If  the  glass  is  not  properly  "seasoned,"  if 
the  "points"  are  not  most  carefully  determined 


Industrial  type 
o  f  thermometer 
to  750°  Faht.  for 
determining  tem- 
perature of  super- 
heated steam. 


and  if  the  scale  is  not  accurately /hYMedy  thkrmsiJumenc  is  more 
than  useless. 

An  accurate  fever  thermometer  is  of  untold  value  in  a  house, 
hospital,  travelling  kit,  or  whatnot,  but  an  inaccurate  one  is  a 
positive  danger  to  the  owner. 

Thermometers  for  specific  purposes  have  to  be  manufactured 
in  a  certain  manner,  both  as  regards  their  style  and  adjustment. 
A  thermometer  is  always  a  thermometer,  but  it  is  impossible  to 
make  a  single  thermometer  to  cover  a  multitude  of  purposes. 
For  instance,  a  thermometer  used  to  indicate  room  temperatures 
is  quite  impracticable  as  a  thermometer  for  indicating  the  tem- 
perature of  the  various  mixtures  used  in  candy  making. 

Thermometers  are  used  in  the  manufacture  of  asphalt,  candy, 
coal,  oil,  wood  drying,  tobacco,  milk,  artificial  teeth,  dough,  ham, 
ice  cream,  maple  and  ordinary  sugar,  and  are  used  in  connection 
with  babies'  food,  the  bath,  brewing,  incubating,  cold  storage, 
fruit  evaporating,  hop  curing,  milk  testing,  photography,  the  soil, 
hot  water  heating,  milk  pasteurizing  and  sterilizing,  orchards, 
railway  coaches,  refrigeration,  veterinary  work,  vulcanizing,  and 
a  thousand  and  one  other  purposes,  each  one  being  of  special 
design  and  especially  adapted  for  its  individual  use. 


FOR  THE  AMATEUR 

By  P.  R.  Jameson,  F.  R.  Met.  Soc. 

"Practical  Hints  for  Amateur  Weather  Forecasters."  Twenty  pages 
illustrated  of  information  on  the  care  and  exposure  of  barometers, 
how  to  set  for  sea  level,  effect  of  temperature  on  the  weather,  etc., 
Beaufort's  scale  of  winds,  general  indications  and  approximate 
forecast  for  the  whole  of  the  barometer  scale,  for  either  rising  or 
falling  indications. 

10  cents  postpaid,  stamps  or  silver 

"Humidity,  Its  Effect  on  our  Health  and  Comfort."  Twenty-four  pages, 
illustrated  on  matters  concerning  the  necessity  of  correcting  present 
day  inside  moisture  conditions  which  are  dangerous  to  health  and 
deprive  us  of  ordinary  comfort.  Hygrometer  and  dew  point  tables 
included  in  this  book. 

10  cents  postpaid,  stamps  or  silver 

"The  Mountains  of  Cloudland  and  Rainfall."  Twenty-four  pages,  illus- 
trated with  different  types  of  clouds  and  ancient  and  modern  rain 
gauges.  The  matter  of  rainfall  is  dealt  with  in  a  very  concise 
manner.  Information  is  given  on  the  variety  and  speed  of  clouds, 
with  their  elevation.  Different  specimens  of  clouds  are  described,  so 
it  will  be  quite  easy  for  any  observer  to  quickly  recognize  them. 
A  page  of  "Weather  Lore"  fittingly  concludes  this  interesting  book. 
10  cents  postpaid,  stamps  or  silver 

"The  Thermometer  and  Its  Family  Tree."  Twenty-four  pages,  illus- 
trated with  thermometers  from  the  time  of  their  invention  to  the 
present  day.  The  history  of  the  birth  and  development  of  this  inter- 
esting instrument  is  popularly  dealt  with  and  the  different  scales  in 
use  on  all  types  of  instruments  are  clearly  described.  The  manu- 
facture of  thermometers  is  described  in  plain  language,  including 
the  manufacture  of  the  glass  from  which  they  are  made. 
10  cents  postpaid,  stamps  or  silver 

"Weather  and  Weather  Instruments."  Second  and  Revised  Edition. 
164  pages  profusely  illustrated.  Written  in  the  simple,  unscientific 
language  of  the  layman,  conveying  a  clear  idea  of  this  absorbing 
subject  to  anyone  of  ordinary  mental  capacity,  even  though  pre- 
viously unacquainted  with  so  attractive  a  study.  Chapters  on 
clouds,  fogs,  weather  map,  frost,  dew,  snow,  rain,  cyclones,  barom- 
eters, humidity,  thermometers,  thunder,  etc.,  etc. 
Cloth  cover  $1.00;  paper  cover  50c  postpaid,  stamps  or  silver 

24 


YB  09734 


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UNIX^ERSITY  OF  CALIFORNIA  LIBRARY 


